In aircraft propulsion systems liner panels are used to isolate the hot gas stream from casings and form a guided path for the cooling air flow. The liner is supported and held in position by supports referred to in this document as hangers. The hangers span the gap between the liner and the case. The air in this gap is used to supply cooling air to cool the liner panel. The cooling air in the cooling passage is at a higher static pressure than the main core streams (inside the liner panel) so the cooling air flows from the cooling air side to the core stream side.
In aircraft propulsion systems liner panels are usually tubular in shape and the gas pressure is contained by hoop stress in the skin of the liner panel. Hangers then simply locate the tube and carry the weight of the tube.
In certain applications the liner panel may not be tubular but may be flat or may transition from round to a polygon.
Liners having these shapes however do not resist the pressure of the gas stream by generating hoop stress in the liner as does a tubular section. The pressure must be reacted though hangers which can transmit the load to the casings.
The exhaust duct for a gas turbine engine is conventionally a circular duct which connects to the turbine stage outlet of the engine. The use of a circular duct is convenient since it can be readily connected to the turbine outlet of the engine. In addition, thermal expansion of the exhaust duct resulting from the heat of the exhaust gas flow may be readily accommodated by the radial growth of the exhaust duct.
However, in many gas turbine engine installations it is desirable for the exit portion of the exhaust duct to be non-circular because this can make the mechanical installation of the exhaust duct into its supporting structure easier and more convenient.
In particular it is advantageous for the exhaust duct to be rectilinear in cross-section to facilitate the mounting of the exhaust duct within its surrounding structure.
Due to the need to accommodate dimensional changes in the exhaust duct resulting from the hot exhaust gases passing through the exhaust duct it is known to provide a duct mounting arrangement that independently accommodates both axial and lateral growth of the exhaust duct resulting from thermal expansion of the duct. Such mounting arrangements are required to accommodate movement of the duct both axially and laterally and can be mechanically complicated.